The present invention relates to a three-port fluid selector valve and particularly to a fluid selector valve having a large flow coefficient while a structure of the valve is compact.
As a three-port fluid selector valve, there is a conventionally and generally known valve for selectively allowing fluid such as liquid which has flowed from an inlet port into a valve chamber to flow out of two outlet ports on opposite sides. In this type of fluid selector valve, there are the following problems when valve seats communicating with the two outlet ports are respectively provided to a wall of the valve chamber into which the fluid flows from the inlet port and a poppet-type valve body disposed in the valve chamber is selectively seated on the valve seats to connect the inlet port to one of the outlet ports and to close the other of the outlet ports.
In other words, in the fluid selector valve, cross-sectional areas of a flow path extending from the inlet port to the valve chamber and the valve chamber itself are increased in a possible range so as to increase a flow rate without upsizing an outside shape. However, as a result of various experiments, arbitral upsizing of the flow path does not effectively increase the flow rate and may produce a contrary effect in such a manner that a stagnating portion or a portion where a flow path section is changed sharply to disturb a flow is formed. Therefore, it was found to be possible to sufficiently enhance the flow coefficient sufficiently by minimizing sharpness of throttles in portions where sharp throttles are formed locally and specifically in a portion where a sharp throttle is formed by projection of a portion of the valve body at a back portion of the valve body into the flow path, sharp throttle portions formed due to provision of the valve seats, and the like.
The present invention has been accomplished based on the above-described findings and it is basically a technical object of the invention to form the above-described three-port fluid selector valve with a large flow coefficient while making a structure of the valve compact.
It is another technical object of the invention to minimize sharpness of a sharp throttle due to projection of a portion of a valve body at a back portion of the valve body and throttles at valve seats to enhance the flow coefficient of the fluid selector valve based on the above findings.
It is another technical object of the invention to provide a fluid selector valve having the enhanced flow coefficient and a structure which can be manufactured and assembled easily.
To achieve the above objects, a fluid selector valve of the invention is a three-port fluid selector valve for selectively allowing fluid which has flowed from an inlet port into a valve chamber in a valve casing to flow out of two outlet ports on opposite sides of the inlet port, valve seats communicating with the respective outlet ports being respectively provided in positions of a wall of the valve chamber facing each other and a poppet-type valve body for connecting the inlet port to one of the outlet ports while closing the other of the outlet ports by being selectively seated on the two valve seats being disposed in the valve chamber, wherein the respective valve seats are respectively provided to inner bottom portions of valve seat holes formed on the valve chamber wall and a depth of each the valve seat hole is equal to or greater than a half of a thickness of an outer peripheral portion of the valve body.
In the fluid selector valve of the invention, it is more appropriate that a part of the wall of the valve chamber and a part of a hole peripheral wall of each of the two valve seat holes are formed of a continuous partial cylindrical face on a side opposite to the inlet port and that a width s of a valve seat step which is a difference between an inside diameter D of each the valve seat hole and an inside diameter d of each the valve seat is sxe2x89xa60.03d+3[mm]. It is more appropriate that elbow-shaped bends of the flow paths extending from the two valve seats to communicate with the respective ports are formed and that a radius R of curvature of each the bend on an outer peripheral side is R=0.5 d to 1 d.
In a preferable embodiment of the invention, the valve casing is formed by joining an end block to a main body, the main body includes a flow path extending from the inlet port to communicate with one of the outlet ports through one of the valve seats, a rod passing for sliding through the main body and having at a tip end of the rod a valve body so as to open and close the valve seats with the valve body, and driving means for driving the rod to seat the valve body on both the valve seats, and the end block has the valve seat communicating with the other of the outlet ports and a flow path extending from the valve seat to the outlet port.
The fluid selector valve of the invention having the above structure selectively allows fluid which has flowed from the inlet port into the valve chamber in the valve casing to flow out of the two outlet ports on opposite sides of the inlet port. Because the valve seats provided in the flow paths extending to the outlet ports are provided at the inner bottom portions of the valve seat holes and each of the valve seat holes has the depth which is equal to or greater than the half of the thickness of the valve body, the back portion of the valve body seated on the valve seat does not project by a large distance into the flow path of fluid flowing through the other valve seat, and the sharp throttle is not formed in the flow path at the back portion. Therefore, it is possible to minimize sharpness of the throttle due to the valve body and to enhance the flow coefficient of the fluid selector valve.
In other words, if the valve seats are respectively provided on inner surfaces of opposite walls facing each other in the valve chamber so as to simplify the structure, the back portion of the valve body itself seated on the valve seat projects into the valve chamber to sharply reduce the flow path of the fluid flowing from the inlet port through the open valve seat. However, such a problem is solved by the above-described structure.
In the fluid selector valve, it is effective to form the inner wall face of the valve chamber and the peripheral wall faces of the two valve seat holes of the continuous partial cylindrical face at a portion of the valve chamber wall facing the inlet port so as to facilitate processing of the valve chamber in the valve casing and to reduce the change of the flow path section. It is effective to minimize the width s of the valve seat step in the above-described range so as to suppress reduction of the flow coefficient due to throttling of the flow paths at the valve seats. Furthermore, by setting the radius R of curvature on the outer peripheral side of each of the elbow-shaped bends of the flow path extending from the two valve seats to communicate with the respective ports in a value in the above-described range, it is possible to further suppress reduction of the flow coefficient.
With the above structure, the fluid selector valve can be formed to have the large flow coefficient while the structure of the valve is made compact.
If the valve casing in the fluid selector valve is formed by joining the end block to the main body and the other valve seat facing one valve seat provided to the main body is provided to the end block, it is possible to easily carry out processing of the valve chamber and the valve seat in the main body and assembly of the valve body and the like through a hole of the main body closed with the end block.